Williams has shown signs of being a capable Plan B during spring practices, which concluded Thursday with the end of a three-day mandatory minicamp.

Bills cornerback Aaron Williams had reservations when new defensive coordinator Mike Pettine first outlined the plan to switch him to safety.

After two inconsistent seasons in Buffalo during which Williams struggled to secure a starting job, he initially wondered whether the position change was a reflection of his performance. Williams' second concern was how quickly he could pick up the new role and its expanded responsibilities of calling plays and making on-field adjustments.

"Oh, man, at first, I was like a chicken with a cut-off head," Williams said. "But I never back off any challenge. You're put in the fire, just roll with it."

As it turns out, the new job just might be a more natural fit for Williams, who is providing the Bills safety in numbers filling the starting spot left open by Jairus Byrd's offseason-long absence.

Though Buffalo retained Byrd's rights by designating him their franchise player in March, the two-time Pro Bowl player has yet to sign the team's one-year contract offer while attempting to negotiate a long-term deal.

Williams has shown signs of being a capable Plan B during spring practices, which concluded Thursday with the end of a three-day mandatory minicamp.

He had an interception in each of the three practices, capped by Williams under-cutting a route to pick off rookie EJ Manuel in the end zone.

"Yeah, that's what they're expecting me to do," Williams said. "It's me being consistent, making plays every day, not just every once in a while. So I'm changing my attitude toward this year, and looking for a better season."

Williams endured what he called "ups and downs" since Buffalo selected him out of Texas in the second round of the 2011 draft.

He had a promising rookie season, in which he had an interception and forced fumble in starting six of nine games. Williams did miss five games because of a chest injury.

He took a step back last year, despite starting 10 of 11 games. Struggling in coverage, he finished with no interceptions, was credited with just seven passes defended, and missed five games after hurting his right knee.

"I think it was one of those years that tested my character: how I handle bad situations; how I handle adversity," Williams said. "I know what it feels like to be on the upside and also the downside. I've pretty much matured and became a veteran player, I can say."

Pettine has faith in Williams, and said the positional switch had nothing to do with performance or Byrd's absence.

"It's a move we were going to make," Pettine said.

In his previous stint as the New York Jets defensive coordinator, Pettine had Williams listed as a safety coming out of college. He also noted that Williams' 6-foot, 200-pound frame combined with his sideline-to-sideline range is better suited for the defense he's installing in Buffalo.

"If you can have a safety that has corner skills, that to me is ideal," Pettine said, noting the NFL is trending toward more of a passing than running style of offense. "I would sacrifice the ability to be a 'box player,' a thicker guy and a thumper type: I'd sacrifice that for the cover skills any day."

He's pleased with how quickly Williams has picked up the new position: "I'd say he's ahead of schedule." And Pettine noted Williams can now fill two roles — safety and cornerback — in a defense that demands versatility from its players.

The Bills' defensive backfield is young and unsettled, especially minus Byrd, a four-year starter. Cornerback Stephon Gilmore, the team's 2011 first-round pick, is the only other returning starter.

Williams isn't sure how his role might change once Byrd arrives.

"Really, to be honest with you, that's above my pay scale," he said.

He's instead relying on the advice former teammate George Wilson provided this offseason, when Williams expressed concerns about switching roles.

"He said, 'It's something you can't be concerned about. Focus on what your responsibilities are,'" Williams said, referring to Wilson, who signed with Tennessee after being cut by the Bills.

"I thoroughly thought about that," Williams said. "I can't really help that they want me at safety. That's where they felt like the team needed me."